The extraordinary power of quantum computation stems from the exponentially large amount of information that can be associated with the entanglement in multi-qubit systems.[1]}
This implies that quantum information is in principle only useful if it can stay perfectly coherent for the whole duration of a computation.
However, every physical qubit is embedded in a noisy environment and the required access to qubit control unavoidably couples the qubit to this environment.
The coupling converts coherent superposition states into statistical mixtures and this loss of quantum coherence in the system directly translates to errors in the quantum information.
